1. Field of the Invention
The present invention relates to a needle plate of a sewing machine mounted on an upper surface of a bed of a sewing machine, and, in particular, to a needle plate of a sewing machine that can smoothly feed a fabric that generates high friction, such as a non-slip fabric, a leather fabric, or a plastic fabric.
2. Description of the Related Art
A needle plate, which is mounted on an upper surface of a bed of a sewing machine, includes a support surface for supporting a fabric, a needle opening through which a needle passes, and a feed dog slot through which a feed dog moves up and down and back and forth. A presser foot presses the fabric against the support surface, and the feed dog, which moves up and down and back and forth through the feed dog slot, feeds the fabric. During sewing, an operator manipulates the fabric to assist feeding of the fabric.
Needle plates used to date have had a support surface that is smooth over its entire area so that an operator can smoothly manipulate a fabric during sewing. Moreover, a surface coating is formed on the smooth surface.
Typically, the surface coating is formed via electroless nickel phosphorus PTFE composite plating, which is performed by using nickel as a basis metal, co-depositing PTFE (polytetrafluoroethylene) particles, and heat-curing the co-deposited layer.
It is well known that such a support surface can reduce the friction between the support surface and a fabric that is being fed over the support surface, due to the presence of a self-lubricating coating formed via electroless nickel phosphorus PTFE composite plating (see, for example, Japanese Registered Utility Model No. 3069939).
The needle plate described in Japanese Registered Utility Model No. 3069939, which has a self-lubricating coating formed via electroless nickel phosphorus PTFE composite plating on its support surface, is effective for sewing an ordinary fabric. However, the needle plate has a problem in that fabric feeding and fabric manipulation are not improved when it is used for a fabric having high adherence to a smooth surface, such as a non-slip fabric, a leather fabric, or a plastic fabric, because such a fabric tends to adhere to the support surface and may fail to smoothly slide over the needle plate.
Moreover, a fabric can smoothly slide over the needle plate described in Japanese Registered Utility Model No. 3069939, because the needle plate has the self-lubricating coating. Accordingly, in a case where the needle plate is used for a smooth fabric or an elastic fabric, the fabric may be pulled by the needle and may slide over the support surface when the needle passes through the fabric. As a result, the fabric may be pulled by the needle into the needle opening of the needle plate.
If the needle moves upward from this state, a part of the fabric that has been pulled into the needle opening by the needle is raised together with the needle. Accordingly, an operation of forming an upper thread loop, which is performed by utilizing the friction between the upper thread and the fabric, might not be appropriately performed, and only a small upper thread loop may be formed. As a result, a loop taker may fail to hook the upper thread loop, and a problem of skipped stitches may occur.